$f(x,y)=e^{3x+4y}$

a$)$ Find gradF at the point $(4,-3)$

b$)$ And the direction of steepest ascent of $f$ at $(4,-3),$ Express as a unit vector.

C$)$ Find the magnitude of the change of $f$ in the direction of the vetor in part b$.$

d$)$ Find $(vec(u),f)(y,-3)$ where vec$(u)=($:$\frac{2}{\sqrt[\phantom{2}]{5}},-\frac{1}{\sqrt[\phantom{2}]{5}}$:$)$